Stringers are structural components that are often used to stiffen panels and other structures. With composite panels, composite stringers may be co-bonded, or secondarily bonded, onto the panel to prevent the panel from buckling or otherwise failing when subjected to compressive loads. The combined panel and stringers may then be secured to a substructure.
While stiffeners provide adequate reinforcement of the corresponding composite panel with respect to compressive loads, the stiffener runouts, or areas at which the stringers terminate, may experience disbonding between the stringers and the panel under certain conditions. The sudden discontinuity of the load path, combined with a low composite interlaminar toughness, may result in a structural component that may delaminate or disbond at operational loads.
Traditionally, the disbond potential that exists at the stiffener runout locations of a composite structure has been accommodated via various techniques. For example, the architecture of a composite panel may be designed to move the stiffener terminations to an edge of the panel. However, doing so may negatively affect the cost and weight of the corresponding panel. According to an alternative traditional solution, the disbond may be allowed to occur at operational loads and fasteners used to arrest the disbond. With this solution, extensive certification testing is required and any amount of disbond, even though non-critical, may be disconcerting to a customer.
Another conventional method for controlling disbond at stiffener runout locations includes the use of flat metallic radius fillers secured to the stiffeners at the termination ends. However, these conventional radius fillers are not efficient at arresting the disbond under the flange, and provide no arrest capabilities under a web of a stringer. Relatively large mechanically attached metallic fittings may also be used to transfer loads from stringers into the attached composite structure. A disadvantage of these types of fittings is that the fittings increase the weight of the corresponding structure and may be expensive to install, while not completely suppressing the disbond at operational loads.
It is with respect to these considerations and others that the disclosure made herein is presented.